The present invention relates to fiber optic coupled pressure transducers and, more specifically, to miniaturized pressure measurement apparatus, such as intravascular catheter tip fiber optic pressure sensors.
Measurement of intravascular blood pressure by means of a hollow catheter tube filled with saline solution and attached to an external transducer has been largely supplanted by fiber optic coupled catheter tips incorporating a pressure transducer. The prior art encompassing the latter includes fiber optic pressure sensors in which a light-reflecting, pressure-deformable diaphragm at the end of the catheter tip is spaced a small distance from the end of one or more fibers and modulates the light reflected back through the fibers in accordance with the pressure responsive position of the diaphragm. The present invention is concerned with pressure sensing apparatus of this type which employs a single fiber both for transmitting light to the diaphragm and for carrying the reflected light back to sensing apparatus.
In copending application Ser. No. 902,666, filed Sept. 2, 1986, now U.S. Pat. No. 4,711,246 there is disclosed a single fiber pressure transducer which simulates the function of a fiber bundle by having the fiber end adjacent the diaphragm covered by a light-absorptive coating with a plurality of discrete, light-transmitting openings. A second type of single fiber optical pressure measuring apparatus is described in abandoned application Ser. No. 298,972, referenced in U.S. Pat. No. 4,487,206, the latter relating to a three-fiber embodiment. The single fiber of the abandoned application, as well as the three fibers of the patented embodiment, are bonded to a molded plastic optical lens with a spherically curved surface which focuses the transmitted light on the diaphragm. In both embodiments, the lens has a diameter essentially equal to that of the diaphragm.
The present invention is directed to improvements in single fiber optical pressure transducers wherein light transmitted through the fiber is focused on the deformable, reflecting diaphragm. Objects of the invention are to effect economies in the manufacture of such apparatus and to improve the sensitivity of the device.
Other objects will in part be obvious and will in part appear hereinafter.